ADHD will be diagnosed based on DSM-IV criteria for ADHD combined subtype ADHD. Combined subtype ADHD requires at least 6 of 9 possible symptoms within both the Hyperactive-Impulsive symptom cluster and the Inattentive symptom cluster. This will be assessed using information gathered from the K-SADS-PL interview with either the potential participant or their parent, and from published self- and parent-report ADHD symptom rating scales (Brown, 1996; Barkley, 1998). Predominantly Inattentive ADHD persons will not be included. The Predominantly Inattentive subtype is the subject of much theoretical debate, as it is not clear that these persons represent a unitary disorder, or that they are neurobiologically similar to combined-subtype ADHD (Millich et al., 2001).